Zeolite catalysts, and especially zeolite rho catalysts and their use in fixed bed reactors for conversion of methanol and ammonia to dimethylamine are well known in the art. (U.S. Pat. No. 3,904,738, U.S. Pat. No. 4,683,334, U.S. Pat. No. 4,752,596, U.S. Pat. No. 4,814,503, and U.S. Pat. No. 4,806,689.) The present invention provides an improvement in these catalysts whereby they are blended with one or more microparticulate binders during formation, which renders the catalyst particles attrition resistant and therefore suitable for use in fluidized bed reactor processes. A particularly useful aspect of the invention is the use of these attrition resistant catalysts in fluidized bed reactors for the efficient and cost effective commercial production of methylamine compounds.
Other examples of improved related catalysts are known in the art. Gladrow et al., (U.S. Pat. No. 3,609,103) disclose use of faujasite and a deagglomerated clay such as Georgia kaolin matrix with a silica-alumina cogel to form a cracking catalyst. The use of the clay phase increases the cracking activity, and thus is added as an active component for the cracking chemistry. Elliott (U.S. Pat. No. 3,867,308) discloses a process for preparing hydrocarbon cracking catalysts using a silica sol by first adding mineral acid to adjust pH, and then adding clay and zeolitic components followed by spray drying. These zeolites are typically X or Y zeolites. Increased attrition resistance and activity of the catalyst, compared to the pure H.sup.+ form of the zeolite is disclosed. The process and additive are chosen to increase the activity of the catalyst by adding active components to the formulation. Gladrow (U.S. Pat. No. 4,147,613, U.S. Pat. No. 4,151,119 and U.S. Pat. No. 4,182,693) disclose a hydrocarbon conversion process utilizing catalyst comprising major amounts of silica and minor amounts of zirconia and alumina, bulk alumina and aluminosilicate zeolites. (3-16 wt percent zeolite, 50-85 wt percent inorganic oxide gel, mostly consisting of silica and a minor amount of zirconia and alumina, and 15 to 40 wt percent of a porous absorbent, for instance bulk alumina.) The absorbant is in place to absorb heavy metals present in the petroleum crudes, which can deactivate the zeolite. Increased activity/selectivities for these catalysts compared to a more conventional Y zeolite containing kaolin and a silica-alumina hydrogel is claimed. Lim et al. (U.S. Pat. No. 4,206,085) report an improved abrasion resistant zeolite, prepared from a faujasite type zeolite, hydrated alumina and ammonium polysilicate or silica sol and clay to form microspheres. The use of ball clay is present because the clay has pre-cracking activity which is important in the hydrocarbon chemistry.
Lim et al. (U.S. Pat. No. 4,325,845) describe a method for producing zeolite cracking catalysts using sodium silicate, derived from silica gel, in combination with clay to form catalysts of good attrition resistance. The authors eliminate the alumina from the formulation (pseudoboehmite), claiming it is a source of coking, or deactivation of the catalyst and sodium silicate is substituted for the alumina hydrate. The silicate is added to the ball clay and zeolite to form the final catalyst in order to enhance catalytic activity.
Scherzer (U.S. Pat. No. 4,987,110) claims an attrition resistant cracking catalyst using a molecular sieve (zeolite) having cracking activity, a clay such as kaolin, a silica sol and aluminum chlorohydroxide. In contrast to the present catalysts, the clay disclosed by Scherzer would have significant activity in the methylamines chemistry. Velten et al. (WO 89/01362) claim various zeolites (ZSM-5, ultra stable Y) formulates with binders prepared from amorphous silica, alumina and zirconia, particularly those of colloidal dimensions. Binder formulations include colloidal silica, colloidal alumina, colloidal silica and acid dispersed alumina which may be noncolloidal or colloidal, colloidal silica and colloidal zirconia, or mixtures of these ingredients. Applicants have found that colloidal silicas, aluminas and silica/alumina combinations do not give a satisfactorily attrition resistant rho zeolite at 50 weight percent binder or greater.